Ophthalmological analysis instrument and method

ABSTRACT

An ophthalmological analysis instrument for measuring a topography of a surface of an eye includes a projection apparatus and a monitoring apparatus. The projection apparatus has at least one illumination device and an aperture device. The illumination device has a first light source, which can emit light in a predominantly monochromatic spectrum, it being possible to image an image pattern on a surface of an eye by the aperture device. Images of the imaged image pattern being recordable by the monitoring apparatus, and a topography of the surface of the being derivable from the images, wherein the illumination device has at least one further light source, which can emit polychromatic light in a predominantly visible spectrum.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims the benefit of German Patent ApplicationNo. 10 2011 081 825.1 filed Aug. 30, 2011, which is fully incorporatedherein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The invention relates to an ophthalmological analysis instrument and toan analysis method, in particular for measuring a topography of asurface of an eye, said analysis instrument having a projectionapparatus and a monitoring apparatus, the projection apparatuscomprising at least one illumination device and an aperture device, theillumination device having at least one first light source, which canemit light in a predominantly monochromatic spectrum, it being possibleto image an image pattern on a surface of an eye by means of theaperture device, images of the imaged image pattern being recordable bymeans of the monitoring apparatus, and a topography of the surface beingderivable from the images.

BACKGROUND OF THE INVENTION

In the analysis instruments and topography systems known from the priorart, an eye is generally illuminated with monochromatic light, such asinfrared light for example, so as to avoid dazzling the person orsubject to be examined where possible. Topography systems are thus knownwhich, in addition to measuring a surface of an eye, also enablepupillometric measurements. In particular when the eye is illuminatedwith monochromatic light, which is only partly visible, a contraction ofthe pupil is effectively prevented, and therefore an illumination ofthis type is particularly well suited for pupillometric measurements.Topography systems may, however, also have a plurality of light coloursfor illumination of an eye. For example, Placido rings are thenprojected onto the eye in different monochromatic light colours. This isbasically used for distinction of the rings of the image pattern imagedon the eye and for the sole purpose of determining a topography. Placidorings of this type in different monochromatic light colours consequentlyform the first light source alone. It is further known to examinemeibomian glands under infrared light.

Analysis instruments for measuring topography or what are known as“keratometers” can also be used for non-invasive analysis of a tear filmon an eye. The image pattern projected onto the surface of the eye isrecorded substantially continuously, wherein any break-up in the tearfilm can be identified by a change to the image pattern. In order toestablish the quality of the tear film, a break-up time thereof isgenerally measured. This measurement is likewise carried out byilluminating the eye with infrared light. For example, in addition tothe topography of the surface of the eye, a measurement of a tear filmis also of utmost importance when selecting contact lenses. Furthermore,analysis of a tear film is limited merely to a distribution of the tearfilm over the eye. A disadvantage of the known analysis instrument andmethod is that the possibilities for examining an eye are limited. It istherefore desirable to broaden the examination possibilities of aninstrument of this type so as to obtain further and more detailedmeasurement results where necessary, which can be used for example forimproved contact lens selection and fitting.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to propose anophthalmological analysis instrument and an analysis method which usesan ophthalmological analysis instrument, with which the examinationpossibilities of a topography system are broadened and improved.

This object is achieved in one embodiment of the invention by anapparatus having a projection apparatus including at least oneillumination device and an aperture device, the illumination devicehaving a first light source and at least one further light source,wherein said first light source can emit light in a predominantlymonochromatic spectrum, and said at least one further light source canemit polychromatic light in a predominantly visible spectrum, and saidaperture device can image an image pattern on a surface of an eye; and amonitoring device recording images of the imaged image pattern, whereina topography of the surface being derivable from the images. This objectis also achieved in a second embodiment of the invention by a methodincluding the steps of illuminating the surface of an eye using anillumination device having at least one light source emittingpolychromatic light in a predominantly visible spectrum; imaging animage pattern onto the surface of the eye using an aperture device;recording the images of the imaged image pattern; and determining a tearfilm on the surface of the eye from the images.

The ophthalmological analysis instrument according to the invention, inparticular for measuring a topography of a surface of an eye, has aprojection apparatus and a monitoring apparatus, the projectionapparatus comprising at least one illumination device and an aperturedevice, the illumination device having at least one first light source,which can emit light in a predominantly monochromatic spectrum, it beingpossible to image an image pattern on a surface of an eye by means ofthe aperture device, images of the imaged image pattern being recordableby means of the monitoring apparatus, and a topography of the surfacebeing derivable from the images, wherein the illumination device has atleast one further light source, which can emit polychromatic light in apredominantly visible spectrum.

In addition to the use of substantially monochromatic light or light ofa relatively narrow wavelength range, the further light source makes itpossible to illuminate the surface of the eye with polychromatic,visible light, whereby additional measurements of properties of the eyeand attainment of more accurate measurement results are possible.Compared to monochromatic or infrared light, it is possible to determinea degree of reddening of the eye using polychromatic light. It is alsopossible to measure a thickness of a tear film or of a lipid layer ofthe tear film relatively accurately in a non-invasive manner, sincecoloured interference patterns of the lipid layer can be produced usingpolychromatic light and can be used for measurements of this type.

The first light source may advantageously emit light in a predominantlyinfrared spectrum. Infrared light has a particularly low dazzling effecton the eye to be examined and is easily produced.

It is particularly advantageous if the further light source can emitpredominantly white light. Particularly good colour reproduction can beachieved with white light, which considerably improves measurementaccuracy, in particular when measuring the degree of reddening of theeye and when producing a coloured interference pattern.

In one embodiment, the further light source can be formed from amultiplicity of uniformly distributed light-emitting diodes. Forexample, the light-emitting diodes themselves may form the imagepattern. The light-emitting diodes can thus be arranged in a ring orbehind an aperture, which can project the image pattern onto the eye.The light-emitting diodes which form the further light source can bearranged on the illumination device together with light-emitting diodeswhich form the first light source. It is thus possible to operate therelevant light-emitting diodes separately or together, as required. Anumber of light-emitting diodes of the first light source to a number oflight-emitting diodes of the further light source can be selected in aratio of 1 to 3.

So as to obtain quality images which can be utilised effectively, themonitoring apparatus may have a camera and an objective lens, amagnification of the image being variable by means of the objectivelens. It is thus possible, depending on the type of measurement, toselect a magnification of the objective lens in such a way that theobject to be measured or the property to be measured can be visuallyillustrated such that evaluation of the image and particularly accuratemeasurement results are generally made possible.

To this end, the objective lens may have a magnification changer, bymeans of which at least one lens can be introduced into a beam path ofthe objective lens and removed therefrom. Compared to a variablemagnification adjustment, which is likewise conceivable, a magnificationchanger can be produced particularly easily and cost effectively. It isalso possible to always use constant, standardised magnifications forthe various measurements, which simplifies considerably the measurementsand an evaluation or analysis of the images. At least threemagnifications can advantageously be formed by means of the objectivelens. A first, normal magnification can be used to measure thetopography of the surface of the eye. A second, large magnification canbe used to measure or analyse a tear film. For example, it is possibleto focus on a lipid layer, in particular with shallow depth of field, soas to determine the thickness of said lipid layer. A third, smallmagnification can be used in particular for meibometric examination,since the recording of images of meibomian glands requires an enlargedspacing between the analysis instrument and the eye inter alia.

It is particularly advantageous if, for a beam path of the monitoringapparatus, an opening is formed in the aperture device in an instrumentaxis of the aperture device orientable in the direction of an opticalaxis of the eye. The surface of the eye can thus be illuminated on allsides with the image pattern by means of the aperture device. Forexample, the aperture device can thus be formed from an illuminatingring or a plurality of concentric rings of this type so as to produce aPlacido image pattern. If the instrument axis of the aperture device isoriented toward the optical axis of the eye, the beam path of themonitoring apparatus can extend directly along the optical axis orthereover, so that the eye can be monitored from the front through theopening, thus considerably simplifying pupillometric measurements inparticular.

The analysis instrument may thus also have a dazzling apparatus forexciting a dazzling stimulus onto the eye, the dazzling apparatuspossibly having a dazzling light source and a beam splitter forreflecting the dazzling light source into the beam path of themonitoring apparatus. The eye can thus be dazzled by this dazzlingapparatus, wherein a response of the eye can be recorded at the sametime by means of the monitoring apparatus. For example, a movement ofthe pupil prompted by the dazzling can be recorded and evaluated. Thedazzling apparatus can be operated independently of the illuminationdevice and image patterns produced thereby.

It is further possible to utilise the illumination device and/or thedazzling apparatus for dazzling the eye with the objective of increasingproduction of tear fluid. The formation of a tear film can thus beexamined and measured.

The analysis method according to the invention is carried out using anophthalmological analysis instrument for measuring a topography of asurface of an eye, the analysis instrument comprising a projectionapparatus and a monitoring apparatus, the projection apparatuscomprising at least one illumination device and an aperture device, animage pattern being imaged onto the surface of the eye by means of theaperture device, images of the imaged image pattern being recorded bymeans of the monitoring device, the illumination device having at leastone light source, which emits polychromatic light in a predominantlyvisible spectrum, and a tear film on the surface being determined fromthe images. A particularly accurate examination of the tear film is madepossible in particular by the use of polychromatic, visible light toilluminate the eye and the tear film with the image pattern.

In one embodiment of the method, the analysis instrument may have anevaluation apparatus, by means of which the images are analysed. Theevaluation apparatus may advantageously be arranged in the analysisinstrument itself and can enable processing of the images and avisualised output of the measurement results established by theevaluation apparatus. In particular, the evaluation apparatus maycomprise data processing means, which can also carry out digitalprocessing of the images. It is also conceivable for the data processingmeans to have a data store with a database, wherein the database mayhave comparative data sets of images or measurement parameters. Forexample, simplified conclusions regarding probable measurement resultsor corrections of measurement results can be drawn from comparative datasets of this type, for example as a result of image comparison.Evaluation can be accelerated considerably and measurement accuracy canbe increased further.

Furthermore, a degree of reddening of the eye can be determined from theimages, a proportion of red in a region of the eye being measurable. Ameasurement of this type cannot be carried out using infrared light ormonochromatic light due to the lack of colour reproduction. During themeasurement process, a reddening of the region surrounding the iris ofthe eye can thus be measured by quantification of the red image portionsdue to the good colour reproduction of the polychromatic, visible light.The measurement can be carried out as a comparative measurement, forexample by comparison with a reference image.

A tear film flow can also be derived from the images, a speed ofmovement of particles situated on the surface being measurable. Inparticular with very large magnification, it is possible to focus thetear film such that particles situated in the tear film are visible, forexample dust particles or foreign bodies. Any movement of theseparticles can be tracked and measured with respect to direction ofmovement and speed. The direction in which and the speed at which thetear film flows can be derived from this. This measurement can be usedto determine tear film quality more accurately.

A tear film break-up time can also be derived from the images, wherein achange to the tear film can be measured. A tear film break-up time canbe measured with normal magnification, and the measurement can becarried out under illumination with infrared light or visible light. Theimage patterns projected onto the surface of the eye, such as Placidorings, make it possible to identify any break-up of the tear film, inparticular as a result of a change to the image pattern in question. Abreak-up time of a tear film can be considered to be a basic parameterfor determining quality of the tear film.

Furthermore, a lipid layer on the tear film can be determined from theimages, wherein the lipid layer can be measured by interference colours.A lipid layer is an outer layer of the tear film, wherein a central,aqueous layer and an inner layer adjacent to the cornea (mucin layer)follow after the lipid layer. The lipid layer is approximately 100 nmthick, prevents rapid evaporation of the aqueous layer and is formedfrom a secretion of the meibomian glands. Since the lipid layer is avery thin layer of the tear film, it can be measured very easily usinginterference colours. The eye or the tear film can thus be illuminatedwith polychromatic light, whereby the thickness of the interferencecolours or an interference pattern can be produced on the tear film bymeans of the aforementioned lipid layer. Possible tear film propertiescan thus be determined more accurately.

It is thus possible to determine a lipid layer thickness or thicknessdistribution of the lipid layer as well as the thickness thereof andalso to examine the function of the meibomian glands on the basis of themeasurable amount of lipids. A large magnification may preferably beselected for a measurement of this type.

Further advantageous embodiments of the method will emerge from thedescription of features of the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will be explained in greaterdetail hereinafter with reference to the accompanying drawings, inwhich:

FIG. 1 shows a simplified, schematic sectional view of an embodiment ofan analysis instrument; and

FIG. 2 shows a front view of the analysis instrument.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

An overview of FIGS. 1 and 2 shows an embodiment of an analysisinstrument 10, which is formed basically from a projection apparatus 11and a monitoring apparatus 12 for monitoring an eye 13. The analysisinstrument 10 further comprises an evaluation apparatus 14, in this casewith means (not illustrated in greater detail) for data processing andfor data output as well as a positioning apparatus 15 for positioningthe analysis instrument 10 relative to the eye 13 in three spatialdirections having the direction components x, y and z arranged at rightangles to one another, as indicated symbolically in this case. Theanalysis instrument is positioned in such a way that an instrument axis16 of the analysis instrument 10 coincides with an optical axis 17 ofthe eye 13.

The projection apparatus 11 is formed as a hollow spherical segment 18and comprises a screen aperture 19 and a reflector 20, which are fixedin a housing 21 (indicated schematically) in such a way that areflecting area 22 of the reflector 20 is always spaced from a surface23 of the reflector 20 at the same distance a, thus forming a curvedaperture space 24. The surface 23 of the reflector 20 is highlyreflective, and therefore the aperture space 24 is filled uniformly withlight when a first light source 25 or a further light source 26 isswitched on. The light sources 25 and 26 are each formed fromlight-emitting diodes 27 and 28, which are each arranged in a uniformlydistributed multiplicity in the manner of a ring 29 over a circumferenceof the screen aperture 19 and in the manner of a ring 30 at an opening31 in the screen aperture 19. The screen aperture 19 is basically formedfrom a transparent body 32 having annular aperture elements 33, whichreflect incident light from a light source 25 and/or 26 into theaperture space 24. The image pattern 35 visible in FIG. 2 is thus imagedonto a cornea 34 of the eye 13, wherein the image pattern 35 is recordedby means of the monitoring apparatus 12.

The monitoring apparatus 12 has a camera 36 with an objective lens 37,wherein the camera 36 comprises an optical video sensor 38 inter alia,which is connected directly to the evaluation apparatus 14. Theobjective lens 37 is formed from two lenses 39 and 40, wherein amagnification changer 41 is provided (as indicated in this case by thedouble-headed arrow), by means of which further lenses 42 can be pivotedinto a beam path 43 of the monitoring apparatus 12. It is thus possibleto record and observe the eye 13 in at least three differentmagnifications. A beam splitter 44 of a dazzling apparatus 45 isarranged in the beam path 43 between the projection apparatus 11 and theobjective lens 37, and consists of a prism system 46, but can also beformed from partially transparent, flat mirrors. A dazzling light source47 can be imaged in the eye 13 via the beam splitter 44. A dazzlingstimulus can thus be excited on the eye 13, completely independently ofthe projection apparatus 11, and therefore the response of said eye canbe recorded with the aid of the monitoring apparatus 12, which isavailable in any case, and can also be determined numerically by theevaluation apparatus 14. A special instrument is accordingly no longernecessary for such a measurement.

With regard to the functioning of the analysis instrument 10, thelight-emitting diodes 27 can emit or irradiate light in a predominantlyinfrared spectrum and the light-emitting diodes 28 can emit or irradiatepolychromatic, white light in a predominantly visible spectrum. Thefirst light source 25 is formed by approximately 50 light-emittingdiodes 27, and the further light source 26 is formed by approximately150 light-emitting diodes 28. Within a measurement process, the firstlight source 25 or the further light source 26 can be switched on, asrequired, to illuminate the eye 13. In particular to determine atopography of the eye 13, it is sufficient to use the first light source25 with normal magnification of the objective lens 37. The first lightsource 25 is also used for meibometric examinations, wherein a smallmagnification of the objective lens 37 is selected in this instance anda spacing between the analysis instrument 10 and the eye 13 is enlarged.The further light source 26 is used for analysis of a tear film, inparticular of a lipid layer of the tear film, wherein a particularlylarge magnification of the objective lens 37 is selected. In addition,the dazzling light source 47 is used for pupillometric measurements.

1. An ophthalmological analysis instrument for measuring a topography ofa surface of an eye, said instrument comprising: a projection apparatusincluding at least one illumination device and an aperture device, theillumination device having first light source and at least one furtherlight source, wherein said first light source can emit light in apredominantly monochromatic spectrum, and said at least one furtherlight source can emit polychromatic light in a predominantly visiblespectrum, and said aperture device can image an image pattern on asurface of an eye; and a monitoring device recording images of theimaged image pattern, wherein a topography of the surface beingderivable from the images.
 2. The analysis instrument according to claim1, in which the first light source can emit light in a predominantlyinfrared spectrum.
 3. The analysis instrument according to claim 1, inwhich the further light source can emit predominantly white light. 4.The analysis instrument according to claim 1, in which the further lightsource is formed from a multiplicity of uniformly distributedlight-emitting diodes.
 5. The analysis instrument according to claim 1,in which the monitoring apparatus has a camera and an objective lens, amagnification of the images being variable by means of the objectivelens.
 6. The analysis instrument according to claim 5, in which theobjective lens has a magnification changer, wherein the at least onelens can be introduced into a beam path of the objective lens andremoved therefrom via the magnification changer.
 7. The analysisinstrument according to claim 5, in which at least three magnificationscan be formed.
 8. The analysis instrument according to claim 1, inwhich, for a beam path of the monitoring apparatus, an opening is formedin the aperture device in an instrument axis of the aperture deviceorientable in the direction of an optical axis of the eye.
 9. Theanalysis instrument according to claim 8, in which the analysisinstrument has a dazzling apparatus for exciting a dazzling stimulusonto the eye, the dazzling apparatus having a dazzling light source anda beam splitter for reflecting the dazzling light source into the beampath of the monitoring apparatus.
 10. An analysis method using anophthalmological analysis instrument for measuring a topography of asurface of an eye, said analysis instrument having a projectionapparatus and a monitoring apparatus, the projection apparatuscomprising at least one illumination device and an aperture device, saidmethod comprising: illuminating the surface of an eye using theillumination device having at least one light source emittingpolychromatic light in a predominantly visible spectrum; imaging animage pattern onto the surface of the eye by using the aperture device;recording the images of the imaged image pattern using the monitoringapparatus; and determining a tear film on the surface of the eye fromthe images.
 11. The analysis method according to claim 10, including thestep of analyzing the images using an evaluation apparatus forming partof the analysis instrument.
 12. The analysis method according to claim10, including the step of measuring a proportion of red in a region ofthe eye to determine a degree of reddening of the eye.
 13. The analysismethod according to claim 10, including deriving a tear film flow fromthe images by measuring a speed of movement of particles situated on thesurface of the eye.
 14. The analysis method according to claim 10,including the step of deriving a tear film break-up time from the imagesby measuring a change to the tear film.
 15. The analysis methodaccording to claim 10, including the step of determining a lipid layeron the tear film from the images using interference colours.
 16. Theanalysis method according to claim 15, including the step of measuring alipid layer thickness.